Such a display arrangement is described in U.S. Pat. No. 6,023,372 and is shown in plan view in FIG. 1.
Such an arrangement 10 comprises a housing assembly 16 having a first enclosure 20 containing a circuit for receiving data or images and containing an imaging assembly. The light transmitted by the imaging assembly is relayed via an optical device 14 to the eye of the user, e.g. through a spectacle lens 24. This light duct 14 comprises a transparent rectilinear light relay 26 conveying light along its longitudinal axis A-A′, and a deflector assembly 28 comprising a mirror 30 placed on a surface that is inclined relative to the first axis A-A′ and an aspherical lens 32 whose axis of revolution B-B′ is, in this example, perpendicular to the first axis A-A′, and is disposed in register with said inclined wall. The housing assembly 16 is mounted on a temple 34 of the spectacle frame by a clamping assembly 36.
The duct presents a given maximum height Hmax beyond the thickness of the lens, and a given mean length Lmoy along its longitudinal axis A-A′. By way of example, such a prior art light duct presents a maximum height Hmax of 11 millimeters (mm) and a mean length Lmoy of 32 mm.
It is known to fabricate the light duct 14 by sticking together a plurality of plastics parts molded out of polymethylmethacrylate (PMMA), or out of “Zeonex” (a cyclo-olefin polymer). These various parts include the light relay 26 which is made by cutting a rectangular section bar out of a plate and then machining and polishing it at its ends, the bar also serving to carry the mirror 30 and the likewise-molded lens 32 which are bonded thereto by adhesive.
Such a method of fabrication is complex since it includes numerous steps of processing, cutting, machining, polishing, and bonding that require very great precision throughout those steps. It is consequently lengthy and expensive.